1. Field of the Invention
This invention relates broadly to endoscopic instruments. More particularly, this invention relates to electrocautery probes for use with a resectoscope.
2. State of the Art
Electrosurgical resection is a procedure in which damaged or enlarged tissue is excised with an electrocautery probe. Transurethral resection is an electrosurgical procedure in which a portion of the prostrate is excised by means of an instrument passed through the urethra. Endometrial ablation is an electrosurgical alternative procedure to hysterectomy for women with menorrhagia (abnormal or excessive uterine bleeding). In both procedures, the instrument typically used is called a resectoscope or hysteroscope. Prior art FIG. 1 shows a typical resectoscope 10 with an electrocautery probe 12. The resectoscope 10 includes a distal guide tube 14 and a body 16 having a stationary handle portion 17 and a movable handle portion 19. A scope 18 is inserted through the guide tube 14 and is provided with a proximal eye piece 20 for viewing the interior of the bladder or other operative site. The scope has a longitudinal axis L. The cautery probe 12 has a distal electrode 22 which is mounted between a pair of arms 23, 25 and is situated in front of the scope 18. The arms 23, 25 extend proximally on either side of the scope and angle downward to be joined at their proximal ends to an electrode lead 27 situated beneath the scope. The electrode lead 27 slidably extends through the housing where at its proximal end the electrode lead is coupled to a wire 24 which is further coupled to a source of cautery current (not shown). A mounting sleeve 29 is provided on the probe 12 for slideably coupling it to the guide tube 14. The mounting sleeve 29 is typically located at the point where the arms 23, 25 are joined to the electrode lead 27. The stationary and movable handle portions 17, 19 are generally capable of axially sliding the probe 12 and its distally mounted electrode 22 relative to the guide tube 14.
The resection procedure involves applying a cauterizing current to the electrode 22 and moving the electrode slowly through or over the prostate or endometrium while viewing the tissue through the scope 18. Thermal energy is applied through the electrode to the prostate or the endometrium so that tissue is excised. The resectoscope and cautery probe are also useful in other procedures for resecting the uterus, ureter, or renal pelvis.
Known electrodes for use in resectoscopes are available in many different shapes and sizes. U.S. Pat. No. 4,917,082 to Grossi et al., for example, discloses several embodiments of a resectoscope electrode including a coagulating electrode, a knife electrode, a punctate electrode, and a roller electrode, among others. Electrodes for use with resectoscopes are also widely available from Olsen Electrosurgical, Inc., Concord, Calif. They are available as blades, needles, balls, loops, spear tips, flexible wires, semi-circular wires, hooks, spatulas and blunt tips.
While differently shaped electrodes are utilized for various different procedures, electrodes of a given shape have a useful surface area limited by the space between the two arms on which they are mounted, and the space between the two arms is limited by the openings through which the instrument is inserted to reach the surgical site. A small surface area, however, compromises the effectiveness of the electrode as a coagulating tool. Thus, in a prostatic resection procedure, it is not uncommon that 80% of the time devoted to the procedure is used to coagulate the prostate and stop it from bleeding. In addition, in many procedures it would be desirable if a single electrode could be sufficiently versatile so as to adequately perform resection, general coagulation, spot coagulation, and tissue sculpting. However, known electrodes are not so versatile, and often multiple electrodes must be used in a single procedure to perform the different functions.
Another difficulty encountered in procedures utilizing electrocautery probes is when the electrocautery probe is moved distally relative to the scope, the arms of the probe tend to occlude the view of the physician through the lens of the scope of the areas lateral of the arms and the electrode. However, procedures utilizing a resectoscope are often involved in resecting and coagulating very delicate tissues in the narrow confines of the urinary and reproductive tracts, and the lower alimentary canal. Therefore, it is important for the physician to have, as much as possible, an unobstructed view through the scope.
One conceivable manner of reducing view obstruction, which is the subject of this invention as disclosed in great detail hereinafter, is to utilize an electrocautery cautery probe having only a single arm to thereby provide greater visibility to the surrounding tissue and to the points of contact between the electrode and the tissue. While the prior art literature does include a few probes having a single arm, it would appear that no commercial devices have incorporated these designs because the designs of the literature include substantial drawbacks. In particular, the single arm probes of the prior art have restricted use and are not at all versatile. For example, U.S. Pat. No. 5,007,907 to Nishigaki et al. discloses an electrocautery probe with a single probe arm having a centrally mounted full loop electrode. The probe arm extends along the top of the scope and does not join an electrode lead, but rather is provided with a female threaded portion for electrically coupling to a male threaded portion of an electrode driving shaft. This unconventional configuration diminishes the desirability of the probe, as typical resectoscopes are adapted for slidably receiving an electrode lead beneath the scope and resectoscopes are not provided with driving shafts having threaded couplings. Therefore, the single armed electrocautery probe of Nishigaki et al. cannot be used with standard resectoscopes.
U.S. Pat. No. 5,196,011 to Korth et al. ostensibly also shows an electrocautery probe with a single arm having a triangular-shaped full loop electrode centrally mounted on the arm and also having a depth gauge coupled to the arm. However, no connection is shown between the probe arm and the resectoscope. Therefore, one can speculate that the probe arm is arguably side mounted, as shown with respect to the multiple arm embodiments in Korth et al., or is top or bottom mounted with no enablement being provided for those possibilities. If the electrocautery probe is intended to be side mounted on the resectoscope, the electrode, being centrally mounted on the probe, would be located substantially off center from the scope, and, as a consequence, a lateral portion of the electrode would be out of view of the physician. Such an electrocautery probe would be dangerous to use because, as stated above, the physician requires a clear view of the tissue coming into contact with the electrode. If the electrocautery probe is intended to be top mounted, i.e., in vertical alignment with a longitudinal axis of the scope, the probe would not be usable with standard resectoscopes. If the electrocautery probe is intended to be bottom mounted in alignment with a longitudinal axis of the scope of the instrument, the electrode would extend too low, out of the view of the physician. As a result, utilization of the non-enabled single arm embodiment of Korth et al. is problematic regardless of how mounted.